1. Field of the Invention
The invention relates to a process for the continuous preparation of organosilanes by hydrosilylation in the presence of an iridium compound as catalyst and free diene as cocatalyst.
2. Description of the Invention
Substituted alkylsilanes are of tremendous economic importance in many fields. They are used, for example, as adhesion promoters or as crosslinkers.
The platinum- or rhodium-catalyzed hydrosilylation of unsaturated compounds has been widely studied in the past. The product yields are often very low, being only 20–45%, which is attributable to considerable secondary reactions.
Iridium catalysts containing diene ligands are, according to U.S. Pat. No. 4,658,050, used in the hydrosilylation of allyl compounds with alkoxy-substituted silanes. JP-A-07126271 describes the hydrosilylation of allyl halides using chlorodimethylsilane in the presence of iridium catalysts containing diene ligands. Disadvantages of these processes are either moderate yields, an uneconomically high catalyst concentration and/or a very short catalyst life. Although EP-A-1156052 and DE-C-10053037 describe the addition of additional diene ligands to increase the catalyst life, the processes in all cases mentioned are batch processes which are subject to very unfavorable preconditions both from an economic point of view and an engineering and safety point of view because of the strongly exothermic character of hydrosilylation reactions, which creates the risk of the reaction becoming “dormant” and later starting up again with a sudden, extremely high generation of heat and pressure.